Glass enameling of aluminum metal matrix composites.

Abstract

To provide a method of forming an enameled coating on a structure made of a metal matrix composite (MMC) material.SOLUTION: In some examples, the method includes providing a structure formed of the MMC material, the MMC material having a given coefficient of thermal expansion (CTE). An enamel mixture is formed to include a glass material and a pigment material, the material selected to yield a mixture with a substantially similar CTE. A surface of the MMC structure is coated with the enamel mixture, the structure then heated in order to melt the enamel mixture. Following the heat treatment, the heated, coated MMC structure is cooled, thereby achieving a glass enameled coating with a color corresponding to the selected pigment.SELECTED DRAWING: Figure 1

Description

[Background technology]

[0001] Many types of electronic devices are portable, "handheld" mobile devices. To protect the electronic, communication, and display components of such devices, the external housing (e.g., chassis, case, shell, etc.) of the device must be designed to be rugged and resilient, yet thin and lightweight.

[0002]

[0002] Designing an attractive, durable, yet thin and lightweight housing often results in a compromise where one or more desired characteristics do not meet expected performance. Thus, there is a need for housing designs that combine durability in a thin, lightweight, aesthetically pleasing package.

[0003]

[0003] The subject matter of this disclosure is directed to avoiding the negative aspects of the above-mentioned problems. Summary of the Invention

[0004]

[0004] According to the present disclosure, a method for forming an enameled coating on a structure made of a metal matrix composite (MMC) material is provided. In some embodiments, the method includes providing a structure formed of an MMC material having a given coefficient of thermal expansion (CTE). An enamel mixture is formed to include a glass frit material and a pigment material, the materials being selected to result in a mixture having a substantially similar CTE. The surface of the MMC structure is coated with the enamel mixture, and the structure is then heated to melt and bond the enamel mixture. After heat treatment, the heated, coated MMC structure is cooled, thereby achieving a glass enameled coating having a color corresponding to the selected pigment.

[0005]

[0005] The needs of conventional approaches are addressed by the methods and devices of the present invention relating to MMC structures (e.g., housings used for electronic devices), and more specifically, to components of MMC structures coated with glass enamel coatings.

[0006]

[0006] These and other features of the present disclosure will become more fully apparent from the subsequent description and appended claims, as set forth hereinafter.

[0007] To further clarify the above and other features of the present disclosure, a more particular description of the subject matter will be rendered by reference to specific embodiments thereof that are illustrated in the accompanying drawings, it being understood that these drawings depict only some embodiments of the subject matter and therefore should not be considered as limiting the scope of the subject matter. [Brief explanation of the drawings]

[0007] [Figure 1]

[0008] FIG. 1 shows a table listing material options for electronic device housing applications, according to aspects of the present disclosure. [Figure 2]

[0009] 2A-2E illustrate exemplary anodized substrates according to the present disclosure. [Figure 3A]

[0010] FIG. 3A illustrates an exemplary glass enameling technique applied to an MMC substrate, according to an embodiment of the present disclosure. [Figure 3B]

[0011] FIG. 3B illustrates an exemplary MMC substrate with a glass enamel coating, with a CTE mismatch between the MMC and the glass enamel coating, according to an embodiment of the present disclosure. [Figure 4-1]

[0012] FIG. 4A shows a table of exemplary enamel mixture compositions for glass enameling of MMC substrates, according to an embodiment of the present disclosure. [Figure 4-2]

[0013] 4B and 4C illustrate examples of MMC housings with enameled coatings according to embodiments of the present disclosure. [Figure 5]

[0014] FIG. 5A illustrates an MMC substrate having an exposed surface according to an embodiment of the present disclosure, and FIG. 5B illustrates the MMC substrate of FIG. 5A after application of an enamel mixture and heat treatment according to an embodiment of the present disclosure. [Figure 6]

[0015] 1 is a flowchart illustrating an exemplary method 100 for enamel coating an MMC material, according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0008]

[0016] The figures are not necessarily to scale. Where appropriate, like or similar reference numbers are used to refer to like or similar components.

[0017] A method for forming an enameled coating on a structure made from a metal matrix composite (MMC) material is provided.

[0009]

[0018] Attention is drawn to Figure 1, which shows a table listing several material options for an electronic housing application. As shown, light gray squares represent preferred values, black squares represent unpreferred values, and medium gray squares represent moderate values. Material options considered include stainless steel, aluminum, magnesium, titanium, Al / SiC-55p MMC, and Al / Al2O3-50p MMC. Material properties considered are the material's mass (g / cc), stiffness, ductility, strength, hardness (compared to other materials), CTE, thermal conductivity, and cost (compared to other materials).

[0010]

[0019] MMC materials may be desirable for use in consumer devices, for example, to limit the bending of the frame (e.g., increase stiffness) while still being lightweight and thin. The stiffness of a material is measured in Pascals (Pa) or Newtons / m 2(At higher levels, it is measured in gigapascals (GPa) or kilonewtons per mm 2 The Young's modulus is given by Young's modulus, measured at 125 GPa (defined as 1 / 2). For purposes of this disclosure, a Young's modulus in the order of 125 GPa provides a sufficiently stiff structural frame for device structures. Some exemplary materials considered, such as Al / SiC-55p MMC, meet or exceed this criterion. Al / SiC MMC materials exhibit densities similar to aluminum but with improved stiffness. Al / SiC materials can be formed using a variety of processes, including, but not limited to, die casting, extrusion, forging, thixoforming, and powder metallurgy.

[0011]

[0020] In some cases, structural elements (e.g., frames) can be used to protect the electrical contents of consumer electronic devices from mechanical damage (e.g., bending, impact, etc.). Steel is an option for such structural frames because it exhibits high stiffness. However, steel also has a high density, which increases the mass of the component. Aluminum is also an attractive material, although its density is significantly lower than steel. However, aluminum's low relative stiffness means that bending can occur. For example, bending electronic components can lead to catastrophic failure, so preventing bending is a primary goal of the structure.

[0012]

[0021] In addition to the need for lightweight, durable structures, various consumer electronic devices (especially military devices) also benefit from structures that provide a desirable degree of stiffness / strength against various environmental factors, yet are lighter in weight than structures made from steel or other high-strength materials.

[0013]

[0022] Titanium has attractive properties for similar chassis applications, but titanium's relative cost is high. Stainless steel has a high mass, which may make it less attractive for small portable devices. Aluminum and magnesium both have low stiffness values. Therefore, MMCs offer a favorable combination of physical properties while being easily tailored to specific applications.

[0014]

[0023] In some examples, Al / SiC is used to illustrate the results of the disclosed techniques and applications. As shown, Al / SiC has a relatively low mass, providing a desirable lightweight frame. It also has a relatively high stiffness, a relatively high thermal conductivity, and a relatively low CTE. Despite challenges with its relative ductility and strength, Al / SiC remains an attractive candidate material for such devices.

[0015]

[0024] As noted in Figure 1, Al2O3 materials are less expensive than Al, which can reduce the blending cost of the MMC. SiC particles are more expensive than Al and can add to the blending cost of the MMC. However, their favorable properties may make such materials a good choice for some applications.

[0016]

[0025] As used herein, a metal matrix composite (MMC) is a material having at least two components—one metal and the other ceramic or organic compound (and / or a different type of metal). MMCs are made by dispersing a reinforcement material in a metal matrix. Some exemplary MMCs use carbon fibers as reinforcement materials with an aluminum matrix to create a composite that exhibits high strength at low density. In another example, an MMC is made of aluminum (Al) impregnated with ceramic particles such as silicon carbide to form an Al / SiC MMC. In some examples, aluminum oxide may be used to form an Al / Al2O3 MMC. Depending on the type of metal (matrix), the chemistry of the reinforcement, the shape of the reinforcement (e.g., particles, fibers, whiskers, etc.), and the ratio of the two components, a variety of useful properties can be engineered. Advantageously, the properties / characteristics of an MMC can be tailored for desired density, stiffness, ductility (elongation), strength, machinability, and / or thermal behavior.

[0017]

[0026] A variety of different MMC materials may be used in the techniques of this disclosure, and the scope of the disclosure is not limited to any particular material or class of materials. The metal matrix can be reinforced with any acceptable type of carbon fiber, ceramic fiber, or ceramic, and the type (and proportion) of reinforcement selected will result in an MMC with specific properties in terms of stiffness and strength.

[0018]

[0027] In the disclosed embodiments, the MMC materials are described with a material content that includes a first metallic material (e.g., aluminum, steel, titanium, magnesium alloy) and a second reinforcing material (e.g., SiC, Al2O4, and / or B4C) present in a second amount (e.g., up to about 55%).

[0019]

[0028] In consumer applications such as portable electronic devices (e.g., cell phones, tablets, etc.), it is desirable for MMC components to be available in a variety of colors. Anodizing techniques are relatively inexpensive and can provide a variety of color finishes for aluminum, magnesium, or titanium materials. However, when used with MMC materials, anodizing produces a dull, matte, and unattractive surface finish. Turning now to the drawings, Figures 2A through 2E illustrate some of the challenges in manufacturing anodized structures. Figures 2A through 2E show images representing anodized substrates (e.g., housings) of various compositions, each representing discontinuities in the anodization for the application. These figures represent an aluminum substrate, 6061Al, and MMC substrates, Al / SiC-55p, Al / Al2O3-50p, Al / Al2O3-30p, and Al / Al2O3-25p, respectively.

[0020]

[0029] In one example, anodizing a housing made of substantially pure Al results in a smooth red surface (e.g., as depicted in FIG. 2A). However, each MMC substrate results in a matte (e.g., rough, broken) finish. In some examples, the anodized layer grows in locations on the surface that substantially expose Al, but not in locations with other grain types. For example, the Al / SiC example of FIG. 2B does not maintain color (e.g., turns gray), and MMC substrates containing Al / Al2O3 accept color, but the color becomes less vibrant with increasing reinforcement concentration (which may be necessary for durability and coating fidelity).

[0021]

[0030] A challenge in enameling MMC materials is that the coefficient of thermal expansion (CTE) of the coating material (e.g., glass) must substantially match the CTE of the MMC substrate material. If there is a large difference in the CTE of the coating material and the MMC substrate material, the coating will tend to separate from the MMC substrate during cooling from the heat treatment due to different shrinkage of the materials. To better match the CTE between the materials, two or more components (provided as frits) can be batched together to produce an enamel mixture or slurry with a CTE equal to or substantially similar to the CTE of the MMC substrate material.

[0022]

[0031] Advantageously, the disclosed process can produce structures with one or more colors while enjoying the mechanical and thermal benefits of MMC structures. In some cases, glass enameling can enhance the effectiveness of coloring and coatings compared to other techniques (e.g., anodizing). In consumer applications, such as electronic mobile devices, the ability to color parts of a structure in a wide range of colors is attractive to manufacturers and customers.

[0023]

[0032] To deliver many desirable properties to MMC substrates, glass enamel processing can be applied to consumer products such as phone chassis. Currently, mobile phone housings are made from aluminum (Al), but MMC offers the opportunity to create a lighter, thinner, and stronger chassis. One challenge with MMC for this application is that although Al can be easily anodized to create products in many colors, anodization is not as effective for MMC materials.

[0024]

[0033] As discussed above, MMC housings exhibit the combination of properties desired for personal device frames, including low mass (similar to aluminum) and high stiffness (similar to steel). However, MMC materials based on aluminum and reinforced with reinforcing components such as SiC and Al2O3 present challenges in maintaining a consistently attractive coating. While some exemplary MMC material housings are shown and described as single rectangles, various other shapes and / or topologies for the MMC material structural elements may be utilized in applications seeking to increase the stiffness and / or strength of the structure (e.g., useful for industrial or military applications).

[0025]

[0034] FIG. 3A illustrates an exemplary glass enameling technique applied to an MMC substrate, as disclosed herein. As shown in FIG. 3A, an enamel mixture / slurry of glass powder 12 is applied to the surface of an MMC substrate 10A. Slurry 12 includes a mixture of one or more frits, such as pigment frit 14 and glass frit 16. As shown, MMC substrate 10A is coated with slurry 12 and heated via heat treatment 18 to melt the frits, producing a glass coating 20 on MMC substrate 10B. While the example of FIG. 3A shows two materials, three, four, five, six, seven, eight, nine, ten, or more materials may be included in the slurry (e.g., as frits).

[0026]

[0035] In some embodiments, slurry 12 can be designed to produce a transparent or translucent coating after firing (e.g., heat treatment 18). Thus, slurry 12 can include glass material frit 16, or a combination of glass materials, such that the resulting glass coating 20 is substantially transparent while providing a protective layer on MMC substrate 10B. However, if so desired, pigment frit 14 can be added to slurry 12, thereby producing a colored coating. In an embodiment, an amount of red pigment (e.g., about 10% by weight of the slurry) is added to the mixture as pigment frit 14, thereby creating a red glass coating 20.

[0027]

[0036] In some embodiments, two or more different glass frits 16 that do not contain pigments are used (e.g., to form a glass material). An advantage of using two or more different glass frits is that glass frits with different CTE values ​​can be selected that collectively approximate the desired CTE and firing temperature for use with a selected substrate. For example, some frits are sold with a description of their CTE and firing temperature (e.g., values ​​shown in FIG. 4A). However, each frit may have a different chemical composition to achieve these properties. Thus, combining frits with different properties can produce desired effects, including the incorporation of pigments, as disclosed herein.

[0028]

[0037] However, combining pigments with glass enameling materials, as described herein, can result in cracked and delaminated coatings if there is a CTE mismatch between the enameling material and the MMC substrate. As shown in the example in Figure 3B, the color can be unevenly distributed across the surface of the MMC frame, indicating crack lines and poorly bonded coatings.

[0029]

[0038] As disclosed herein, if the materials used in the enamel mixture have a CTE that does not substantially match the CTE of the MMC substrate, delamination may occur during cooling. As provided, the CTE of the frit mixture can be tailored by mixing one or more frits together, even using different frits with different CTEs.

[0039] During the enameling process, the coated MMC is fired at a specific temperature designed to melt the frit, thereby adhering the coating material to the MMC substrate. This temperature is selected to be below the solidus temperature of the MMC substrate material (e.g., alloy) to avoid melting the MMC material.

[0030]

[0040] In an exemplary MMC substrate formed from a SiC-reinforced Al alloy, the high Si content in the alloy sets the solidus temperature at approximately 577°C, which may be lower than that of typical Al alloys. Therefore, the frit must be selected to produce an enamel mixture at a firing temperature lower than the solidus temperature of the SiC-reinforced Al alloy.

[0031]

[0041] As disclosed herein, a coating can be applied to one or more surfaces of a structure treated with MMC enamel technology by 1) applying an enamel mixture or slurry (e.g., including glass frit and pigment) to the surface of the structure, and 2) heat treating (e.g., firing) the structure in a furnace.

[0032]

[0042] 4A provides a table of exemplary enamel mixture compositions for glass enameling of MMC substrates as disclosed herein. As shown, the MMC substrates include a SiC / Al content of about 55%. The MMC substrates have a CTE of about 11 and a maximum temperature of about 577°C.

[0033]

[0043] The enamel mixture is composed of frits A and B, with concentrations of approximately 33% and 67%, respectively. Frit A corresponds to a CTE of approximately 9.3 and a firing temperature of approximately 500°C, while frit B corresponds to a CTE of approximately 12.5 and a firing temperature of approximately 560°C. When the enamel mixtures are combined in the percentages shown, the resulting CTE is approximately 11.4 and the firing temperature is approximately 540°C.

[0034]

[0044] As described herein, there is substantial similarity between the CTE of the substrate and the frit mixture. For example, the frit mixture CTE is within a threshold difference (less than 5%, but may be less than 1%, 10%, 15%, 20%, or any other amount to achieve the desired result). Furthermore, the firing temperature of the frit mixture is below the maximum temperature of the MMC substrate.

[0035]

[0045] 4B and 4C show examples of MMC housings 30A and 30B with enameled coatings, as disclosed herein. The MMC housings are each an Al alloy containing a SiC component. As shown, the MMC housing 30A in FIG. 4B has an upper portion 32A and a lower portion 34A, where the upper portion 32A is treated with a 10% pigmented glass enamel mixture and the lower portion 34A is treated without a pigment. The MMC housing 30B in FIG. 4C has an upper portion 32B and a lower portion 34B, where the upper portion 32B is treated with a 10% pigmented glass enamel mixture and the lower portion 34B is treated without a pigment.

[0036]

[0046] The difference in finish between Figures 4B and 4C results from the heat treatment time. Where provided, MMC housing 30A was treated in a particular treatment environment (e.g., ambient air) for a relatively short time (e.g., 5 minutes). MMC housing 30B was treated in the same treatment environment for a relatively long time (e.g., 20 minutes). The darker appearance of top portion 32B of MMC housing 30B indicates a deeper coloration relative to top portion 32A of MMC housing 30A. This is the result of the extended heat treatment time for MMC housing 30B, which allows more time for the enamel mixture to melt, producing a richer color.

[0037]

[0047] Figure 5A shows an MMC substrate with an exposed surface. Figure 5B shows the MMC substrate after an enamel mixture (e.g., including glass frit and pigment frit) has been applied to the MMC substrate and heat-treated. As shown, a substantially consistent glass coating is obtained, displaying a rich, durable color. In particular, the constituent materials of the enamel mixture are selected so that the CTE of the frit combination substantially matches the CTE of the MMC substrate. Therefore, the finished glass coating is less susceptible to delamination during cooling compared to other techniques.

[0038]

[0048] The MMC substrates shown in Figures 5A and 5B can be used in consumer applications such as mobile electronic devices. The ability to color components of device housings in a wide range of colors is an attractive prospect for manufacturers and consumers. The disclosed techniques and coatings can be used in consumer applications where component aesthetics are an important feature.

[0039]

[0049] Additionally, in some embodiments, glass enamel applied to the MMC housing provides a wear and / or corrosion resistant coating in addition to providing color.

[0040]

[0050] FIG. 6 is a flowchart illustrating an exemplary method 100 for enamel coating an MMC material according to the present disclosure. In block 102, an MMC material (e.g., AlSiC-55p) is selected. In block 104, the CTE for the selected MMC material is determined. In block 106, a coating material for the enamel mixture is selected. For example, the type of material (e.g., glass, pigment, etc.) is selected. In the absence of a pigment frit, glass frit alone produces a transparent or translucent coating after heat treatment. However, by adding a pigment frit to the enamel mixture, a colored coating can be achieved. Furthermore, the coating material (and enamel mixture) are selected to ensure that the firing temperature is below the solidus temperature of the MMC material to avoid damage to the MMC substrate.

[0041]

[0051] At block 108, the amount of each coating material is determined. For example, the CTE for the enamel mixture must be within a threshold range of CTE for the selected MMC material. That is, the amount of coating material (e.g., two or more, provided as multiple frits) is determined to produce a suitable CTE. At block 110, the enamel mixture (including the coating materials in a medium such as water) is applied to one or more surfaces of the MMC material.

[0042]

[0052] In block 112, the coated MMC material is subjected to a heat treatment to fuse the enamel mixture. For example, the temperature, length of treatment time, and / or environmental treatment conditions can be determined to achieve the desired results. As disclosed herein, the coated MMC material can be heated in an ambient air environment for between 5 and 20 minutes, or longer, at temperatures up to 600°C. For example, for some enameled coatings, a longer heating time is advantageous, ensuring complete or near-complete melting of the glass frit and producing better color development. In block 114, the coated MMC material is cooled, thereby providing a durable, colored coating on the underlying material.

[0043]

[0053] In some embodiments, the coated MMC material is subjected to one or more additional surface treatments to enhance the protective or aesthetic properties of the finished product.

[0054] In a disclosed embodiment, a method for forming an enameled coating on a structure made of a metal matrix composite (MMC) material includes the steps of providing a structure formed of an MMC material, forming an enamel mixture having one or more glass materials and zero or more pigment materials, coating the enamel mixture on a surface of the MMC structure, heating the coated MMC structure to melt the enamel mixture, and cooling the heated, coated MMC structure to achieve a glass enameled coating.

[0044]

[0055] In some embodiments, the MMC material of the MMC structure has a first CTE, in some embodiments, the glass material has a second CTE, and the pigment material has a third CTE.

[0045]

[0056] In an embodiment, the method further includes selecting a ratio of glass material to pigment material to produce an enamel mixture having a first CTE. In an embodiment, the method further includes selecting the MMC material from Al / SiC or Al / Al2O3.

[0046]

[0057] In some embodiments, forming the enamel mixture includes mixing a glass frit of the glass material and a pigment frit of the pigment material in a liquid medium.

[0058] In some disclosed embodiments, a method for forming an enameled coating on a structure made of a metal matrix composite (MMC) material includes providing a structure formed of the MMC structure including an MMC material having a first coefficient of thermal expansion (CTE); forming an enamel mixture having a second CTE similar to the first CTE; coating the enamel mixture on a surface of the MMC structure; heating the coated MMC structure to melt the enamel mixture; and cooling the heated, coated MMC structure to achieve a glass enameled coating.

[0047]

[0059] In some embodiments, the value of the second CTE is within 10% of the value of the first CTE. In embodiments, the enamel mixture includes a glass material having a third CTE and a pigment material having a fourth CTE, the second CTE being different from the third and fourth CTEs. In embodiments, the enamel mixture includes approximately two-thirds glass material and one-third pigment material.

[0048]

[0060] In some embodiments, the heating step is performed in a furnace at a temperature greater than 500° C. In embodiments, the method further includes selecting the MMC material from Al / SiC or Al / Al 2 O 3 .

[0049]

[0061] In some disclosed embodiments, a structure having an enameled coating is provided, the structure including a structural frame formed of an MMC material containing a metal and a ceramic or organic compound, and an enameled coating on a surface of the MMC material, the enameled coating containing a coating material and a pigment material.

[0050]

[0062] In some embodiments, the coating material is a glass or ceramic material and the pigment material is a colored dye. In some embodiments, the MMC material has a first CTE and the enameled coating has a CTE substantially similar to the first CTE.

[0051]

[0063] In an embodiment, the MMC material includes Al / SiC or Al / Al2O3.

[0064] In an embodiment, the MMC material has a Young's modulus value greater than 125 GPa.

[0065] The following is a non-limiting list of specific advantages and features of the present disclosure:

[0052]

[0066] In the drawings, like features are designated with the same reference characters throughout.

[0067] The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived by applicants. It will be understood, with the benefit of this disclosure, that features described above in accordance with any embodiment or aspect of the presently disclosed subject matter may be utilized alone or in combination with any other described feature in any other embodiment or aspect of the disclosed subject matter. [Explanation of symbols]

[0053] 10A MMC board 10B MMC board 12 Glass powder, slurry 14 Pigment frit 16 Glass frit 18 Heat Treatment 20 Glass Coating 30A MMC housing 30B MMC housing 32A upper part 32B Upper part 34A Lower 34B lower part

Claims

1. 1. A method for forming an enameled coating on a structure made of a metal matrix composite (MMC) material, comprising: Providing an MMC structure formed from an MMC material; forming an enamel mixture having one or more glass materials and zero or more pigment materials; coating the enamel mixture on the surface of the MMC structure; heating the coated MMC structure to melt the enamel mixture; cooling the heated coated MMC structure to achieve a glass enamel coating; A method comprising:

2. 10. The method of claim 1, further comprising selecting an MMC material for the MMC structure having a first coefficient of thermal expansion (CTE).

3. 3. The method of claim 2, further comprising the step of selecting a first glass material having a second CTE.

4. 4. The method of claim 3, further comprising the step of selecting a second glass material having a third CTE.

5. 3. The method of claim 2, further comprising the step of selecting a ratio of said glass material to said pigment material to result in said enamel mixture having said first CTE.

6. 2. The method of claim 1, wherein the Al / SiC or Al / Al ２ O ３ The method further comprises selecting the MMC material from

7. 2. The method of claim 1, wherein forming the enamel mixture comprises mixing a glass frit of the glass material and a pigment frit of the pigment material in a liquid medium.

8. A method according to any one of claims 1 to 7, further comprising the step of selecting the one or more glass materials based on the solidus temperature of the MMC material.

9. 1. A method for forming an enameled coating on a structure made of a metal matrix composite (MMC) material, comprising: providing a structure formed of an MMC structure having an MMC material with a first coefficient of thermal expansion (CTE); forming an enamel mixture having a second CTE; coating the enamel mixture on the surface of the MMC structure; heating the coated MMC structure to melt the enamel mixture; cooling the heated coated MMC structure to achieve a glass enamel coating; Including, the difference between the first CTE and the second CTE is less than 1%, 5%, 10%, 15%, or 20% of the first CTE or the second CTE; method.

10. 10. The method of claim 9, wherein the enamel mixture includes a glass material having a third CTE and a pigment material having a fourth CTE, the second CTE being different from the third and fourth CTEs.

11. 11. The method of claim 10, wherein the enamel mixture comprises two-thirds one glass frit material and one-third another glass frit material.

12. 10. The method of claim 9, wherein the heating step is carried out in a furnace at a temperature above 500°C.

13. 10. The method of claim 9, wherein the Al / SiC or Al / Al ２ O ３ The method further comprises selecting the MMC material from

14. A method according to any one of claims 9 to 13, further comprising the step of selecting one or more glass materials to be contained in the enamel mixture based on the solidus temperature of the MMC material.

15. 1. A structure having an enameled coating, a structural frame formed of a metal matrix composite (MMC) material containing metal and ceramic or organic compounds; an enamelled coating on the surface of the MMC material; wherein the enamelled coating comprises a coating material and a pigment material.

16. 16. The structure of claim 15, wherein the structure is a housing for a consumer electronic device.

17. 17. The structure of claim 16, wherein the coating material is a glass material or a ceramic material and the pigment material is a colored dye.

18. 17. The structure of claim 16, wherein the MMC material has a first coefficient of thermal expansion (CTE) and the enameled coating has a second CTE, and the difference between the first CTE and the second CTE is less than 1%, 5%, 10%, 15%, or 20% of the first CTE or the second CTE.

19. 17. The structure of claim 16, wherein the MMC material comprises one or more aluminum or aluminum alloys.

20. 20. The structure of claim 19, wherein the MMC material is Al / SiC or Al / Al ２ O ３ A structure containing:

21. 17. The structure of claim 16, wherein the MMC material has a Young's Modulus value greater than 125 GPa.

22. A structure described in any one of claims 15 to 21, wherein the coating material is selected based on the solidus temperature of the MMC material.

Images